Magnetic Property of Thin Film of Co-Tb Alloys Deposited on the Barrier Layer of Ordered Anodic Alumina Templates

Abstract

Recently, search for novel materials for bit patterned media (BPM) has been very intense due to their potential application in ultra-high-density hard disk drive. In a quest of finding new materials for BPM, we have taken up to study ordered array of nanostructured Co-Tb alloy. Thin films of Ta (1 nm)/Co1−xTbx (24 nm)/Ta (4 nm) (x = 0.10, 0.15, 0.18 and 0.33) alloys were deposited on the barrier layer of auto-assembled anodic alumina template using dc magnetron sputtering to form a nanostructured array, the so-called nanobump. Similar array of compounds on a flat Si substrate was also deposited for comparison (reference sample). The measurement of room temperature magnetization (M) versus field (H) curve indicates that the coercivity and the squareness [Mr/Ms] of nanobumps as well as reference samples were found to increase with increase of Tb content. However, the values of HC and Mr/MS for nanobumps were found to be higher than those of reference samples. The measurements of in-plane and out-plane M-H curves reveal that Co1−xTbx (x = 0.15, 0.20 and 0.33) nanobumps exhibit magnetic isotropy behaviour. The measurements of temperature variation of magnetization demonstrate that these films exhibit ferrimagnetism with a compensation temperature much above the room temperature.